Unable to update a document

I have created a space and invited User B to that space and assigned Editor rights to User B. I logged into Alfresco as User B and User B updated a document with another document in that space. After updation,User B opened the document,it is showing older one. User B downloaded the document using the download option in view details,it is showing new one. Whats the problem here. How can i open updated new document.